The discovery and design of materials with large thermal conductivities (κ L ) is critical to address future heat management challenges, particularly as devices shrink to the nanoscale. This requires developing novel physical insights into the microscropic interactions and behaviors of lattice vibrations. Here, we use ab initio phonon Boltzmann transport calculations to derive fundamental understanding of lattice thermal transport in two-dimensional (2D) monolayer hexagonal boron-based compounds, h-BX (X = N, P, As, Sb). Monolayer h-BAs, in particular, possesses structural and dispersion features similar to bulk cubic BAs and 2D graphene, which govern their ultrahigh room temperature κ L (1300 W/m K and 2000-4000 W/m K, respectively), yet here combine to give significantly lower κ L for monolayer h-BAs (400 W/m K at room temperature). This work explores this discrepancy, and thermal transport in the monolayer h-BX systems in general, via comparison of the microscopic mechanisms that govern phonon transport. In particular, we present calculations of phonon dispersions, velocities, scattering phase space and rates, and κ L of h-BX monolayers as a function of temperature, size, defects, and other fundamental parameters. From these calculations, we make predictions of the thermal conductivities of h-BX monolayers, and more generally develop deeper fundamental understanding of phonon thermal transport in 2D and bulk materials.

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Discovering new materials with ultrahigh thermal conductivity has been a critical research frontier and driven by many important technological applications ranging from thermal management to energy science. Here we have rigorously investigated the fundamental lattice vibrational spectra in ternary compounds and determined the thermal conductivity using a predictive ab initio approach. Phonon transport in B-X-C (X = N, P, As) groups is systematically quantified with different crystal structures and high-order anharmonicity involving a four-phonon process. Our calculation found an ultrahigh room-temperature thermal conductivity through strong carbon-carbon bonding up to 2100 Wm −1 K −1 beyond most common materials and the recently discovered boron arsenide. This study provides fundamental insight into the atomistic design of thermal conductivity and opens up opportunities in new materials searching towards complicated compound structures.

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The theoretical investigation of heat dissipation for polymer‐bonded explosives (PBXs) is in high demand in explosive design in terms of safety and realibility, particularly as lack of effective experimental measurements. Here, we investigate the fundamental understanding of thermal transport across the heterogeneous interface between HMX and PVDF, by using the diffuse mismatch model and anharmonic inelastic model. This work explores the interfacial thermal conductance via ab initio calculation and derived phonon dispersions, phonon group velocities. For HMX‐PVDF interface, it is shown that low‐frequency phonon modes (especially lower than 10 THz) and two‐phonon elastic processes play dominant roles in the interface thermal transport. Furthermore, we present the calculated interfacial thermal conductance as a function of temperature. The thermal conductivity of mixture HMX‐PVDF system is analyzed with an effective medium approximation model. From these calculations, we give the thermal transport properties predictions of PBX for thermal conductivity enhancement and provides fundamental microscopic insights into phonon transport physics in PBX.

Understanding the thermal transport in polymer-bonded explosives (PBXs) is critical for enhancing the safety and reliability during PBX design, especially in the absence of effective experimental measurements. In this work, we rigorously investigated the phonon properties of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and polyvinylidene fluoride (PVDF) and calculated the interfacial thermal conductance using an ab initio approach. The diffuse mismatch model and anharmonic inelastic model were adopted to examine the interfacial thermal conductance as a function of temperature for the TATB–PVDF interface. Our calculation results indicate that low-frequency phonon modes and the two-phonon process play dominant roles in the thermal transport at interfaces. In contrast, high-order phonon processes involving three to eight phonons accounted for around 8% of the interfacial thermal conductance at the TATB–PVDF interface. Phonon properties, such as the velocity and degree of phonon density overlap, are discussed for the TATB–PVDF and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX)–PVDF interfaces to estimate the interfacial thermal conductance of PBXs. This study provides a theoretical explanation for the establishment of a research method for PBX thermal transport.